The present invention relates to the field of internal combustion engines. In particular, the invention relates to a rocker assembly that provides a variable lift ratio to increase the amount of air entering the combustion cylinder.
Rocker assemblies are well-known in the field of internal combustion engines. Rocker assemblies are responsible for opening and closing intake and exhaust valves in a cylinder head of an engine. Opening of the intake valve allows air to enter the combustion chamber of an engine to provide combustion air for the combustion process. The combustion air is mixed with fuel in the combustion chamber where the mixture is compressed and ignited by a spark plug, or in the case of a diesel engine by the pressure and temperature associated with the compression stage. Once the mixture has been ignited, the combustion of the mixture forces the piston down the cylinder away from the combustion chamber to create a stroke. The gases formed by igniting the mixture are then evacuated from the combustion chamber through an opened exhaust valve.
Performance and efficiency of an engine is related to the amount of air that can be drawn by the intake valve into the combustion chamber, as well as the amount of gas that can be evacuated out of the combustion chamber through the exhaust valves. One approach for increasing air flow into and out of a combustion chamber is to increase the amount of valve lift of the valves. This can be done be replacing the existing rocker arms with higher ratio rocker arms or by replacing the cam with a cam having a steeper lift curve, i.e., a more “aggressive” cam.
Rocker arms multiply the lift provided by a lobe of a camshaft. Increasing the ratio of the rocker arm, increases the multiplication factor. Thus, more air can be drawn into or evacuated out of the combustion chamber, but the aggressiveness of the valve lift is not altered by the higher ratio rocker arms.
Replacing the camshaft with a more aggressive camshaft also increases the lift of the valves. By changing the profile of the lobes on the camshaft, the amount of valve lift and the aggressiveness of that lift can be changed. However, mechanical allowances prevent camshafts from being too aggressive. Additionally, aggressive camshafts are less reliable.
Accordingly, there is a need for a rocker assembly that provides the advantages of both current rocker arms and camshafts without the disadvantages or limitations associated with each.